I was taught that “semi-automatic” means: the weapon fires each time you pull the trigger, without some other action required. Compare with lever action, bolt action, or single action, each of which require at least one other non-trigger pull action.
So a DA revolver is semi-automatic, as is this gun. Now it may be that it skirts some idiot regulations in some state, but that doesn’t justify pretending it is something new, let alone useful.

I was taught that “semi-automatic” means: the weapon fires each time you pull the trigger, without some other action required.

Well, you were taught wrong. A semi-auto is a gun that only fires once per trigger pull AND loads itself when you fire the gun. A double action revolver isn’t semi-automatic because your finger performs the action of “loading” the gun (which, in the case of the revolver, involves advancing the cylinder). In other words, you’re performing a manual action to load the gun/align the cylinder, so it’s not a semi-auto.

Compare a normal DA revolver with something like the Mateba 6 Unica Autorevolver, which uses gas pressure to advance the cylinder and cock the hammer, and so is semi-automatic.

This gun requires a manual action to load the gun, just like a bolt action or a normal revolver, so it’s not a semi-auto.

As for it being useful, many would say that defying would-be tyrants and providing people who live in unfree states an efficient method of self-defense is very useful indeed.

Interesting idea… looks like it fires from an open bolt position, but the trigger’s action is to extract and then release the bolt at the further point of pull. Would work for pistol caliber, but not for rifle length, as others have said.

We could work with this for a rifle design. We’d need a three-stage trigger that has three actions: one to extract, one to reload, and a third to fire the round. We could make this work if the act of firing the rifle does NOT reload the rifle, but instead cocks some kind of extraction and reloading mechanisms, or otherwise my some means store the energy needed for later stages. These first stage of the trigger would extract the expended round and cock the hammer and the second stage to reload the next round. After the first and second stages are released, the trigger should be in the firing position. After firing, the trigger would have to be released all the way back to the first stage position in order to actual the extraction mechanism.

As noted in the video, this would have considerable advantages for a suppressed rifle. If a piston were built into the first chamber of a suppressor, and use the muzzle blast that to load the springs, we could get extra suppressive effect by expanding gasses in the first chamber and extracting work before the gasses go past the first baffle.

Now, how exactly all these will work mechanically with mechanisms working in opposition to each other, I don’t know, but it is an interesting idea to start from.

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